KR20130014278A - Nanowire and method for manufacturing the same - Google Patents

Abstract

PURPOSE: A method for manufacturing a nanowire is provided to form a metal nanowire with small diameter and long length. CONSTITUTION: A method for manufacturing a nanowire comprises a step of adding a metal compound and a capping agent to a solvent(ST20). The first capping agent contains a first capping agent and a second capping agent. The first capping agent contains a polymer of a first molecular weight. The second capping agent contains a polymer with a second molecular weight which is greater than the first molecular weight. The polymers are polyvinylpyrrolidone. [Reference numerals] (ST10) Step of heating a solvent; (ST20) Step of adding a capping agent into the solvent; (ST30) Step of adding a catalyst into the solvent; (ST40) Step of adding metal compounds into the solvent; (ST50) Step of adding a solvent at room temperature into the solvent; (ST60) Step of refining nanowires

Description

Nano wire and manufacturing method thereof {NANOWIRE AND METHOD FOR MANUFACTURING THE SAME}

The embodiment relates to a nanowire and a method of manufacturing the same.

Background Art A transparent electrode using a transparent conductive material has been applied to various electronic products such as display devices, solar cells, and mobile devices. As a transparent conductive material for forming such a transparent electrode, research on nanowires, which are wire-shaped structures having a size of nanometer level, is being actively conducted.

Such nanowires may have excellent electrical conductivity, flexibility, and transmittance such that the transparent electrode may have excellent characteristics. However, the nanowires are easily aggregated in the reaction process to form nanoparticles, thereby decreasing the yield of the nanowires. In addition, when the length of the nanowires are made longer, the diameter becomes thicker, and when the diameter is thin, the length tends to be shorter, which makes it difficult to manufacture long and thin nanowires. Accordingly, there is a difficulty in practical use. In addition, a substance such as a catalyst used to promote the nanowire formation reaction remains on the surface of the nanowires, causing surface oxidation or corrosion, or lowering electrical conductivity.

The example is to provide a nanowire having a small diameter and a long length, and an improved aspect ratio and a method of manufacturing the same.

Method for producing a nanowire according to the embodiment includes the step of heating by adding a metal compound and a capping agent to the solvent to form a metal nanowire. In this case, the capping agent comprises a first capping agent comprising a polymer of the first molecular weight; And a second capping agent comprising a polymer of a second molecular weight greater than the first molecular weight.

In one embodiment, the polymer of the first molecular weight and the polymer of the second molecular weight may be polyvinylpyrrolidone.

In one embodiment, the first molecular weight is 40000 to 80000, the second molecular weight may be 240000 to 450000.

In one embodiment, the ratio of the polymer of the first molecular weight and the polymer of the second molecular weight may be 2: 1 to 8: 1.

In one embodiment, the solvent may be heated to a temperature of 110 ℃ to 140 ℃.

In one embodiment, the metal compound may be a silver compound.

The metal nanowires formed by the nanowire manufacturing method according to the embodiment may have a diameter of 30 nm to 60 nm, a length of 20 μm to 60 μm, and an aspect ratio of 330 to 2000. The metal may be silver.

The nanowire manufacturing method according to the embodiment uses a first capping agent including a polymer having a first molecular weight and a second capping agent including a polymer having a second molecular weight.

In this case, the length of the metal nanowires is increased by the second capping agent having a relatively large molecular weight, and the diameter of the metal nanowires may be thinned by the first capping agent having a relatively small molecular weight.

That is, the metal nanowires may be formed to be thin and long by the first capping agent and the second capping agent. Accordingly, the nanowire manufacturing method according to the embodiment can provide a metal nanowire having a large aspect ratio.

1 is a block diagram illustrating a process of manufacturing a silver nanowire according to an embodiment.
2 is a SEM photograph of the silver nanowires according to the embodiment.
3 is a SEM photograph of a silver nanowire according to a comparative example.

Method of manufacturing a nanowire according to the embodiment includes the step of heating by adding a metal compound and a capping agent (capping agent) to the solvent to form a metal nanowire. In this case, the capping agent comprises a first capping agent comprising a polymer of the first molecular weight; And a second capping agent comprising a polymer of a second molecular weight greater than the first molecular weight.

The polymer of the first molecular weight and the polymer of the second molecular weight may be polyvinylpyrrolidone.

The first molecular weight may be 40000 to 80000, and the second molecular weight may be 240000 to 450000.

The ratio of the polymer of the first molecular weight and the polymer of the second molecular weight may be 2: 1 to 8: 1.

The solvent may be heated to a temperature of 110 ℃ to 140 ℃.

The metal compound may be a silver compound.

By the nanowire manufacturing method according to the embodiment, a metal nanowire having a diameter of 30nm to 60nm, a length of 20㎛ to 60㎛, an aspect ratio of 330 to 2000 can be formed. The metal may be silver.

Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings.

1 is a block diagram illustrating a process of manufacturing a silver nanowire according to an embodiment. 2 is a SEM photograph of the silver nanowires according to the embodiment. 3 is a SEM photograph of a silver nanowire according to a comparative example.

Referring to Figure 1, the nanowire manufacturing method according to the embodiment, heating the solvent (ST10), adding a capping agent to the solvent (ST20), adding a catalyst to the solvent (ST30), to the solvent The method may include adding a metal compound (ST40), adding a solvent at room temperature to the solvent (ST50), and purifying the nanowires (ST60). Not all of these steps are necessary and depending on the manufacturing method, some steps may not be performed and the order of each step may be changed. Each step described above will be described in more detail as follows.

In the step of heating the solvent (ST10), the solvent is heated to a reaction temperature suitable for the formation of the metal nanowires. The reaction temperature may be about 110 ℃ to about 170 ℃. In more detail, the reaction temperature may be about 110 ° C to about 140 ° C.

A polyol may be used as the solvent. Such polyols can serve to form metal nanowires by acting as a mile reducing agent together with a solvent for mixing different materials. Examples of such polyols include ethylene glycol (EG), propylene glycol (PG), diethyl glycol, dipropylene glycol, 1,3-propanediol, glycerin, glycerol, glucose and the like. . The reaction temperature may be variously adjusted in consideration of the type and characteristics of the solvent and the metal compound.

Next, in the step of adding a capping agent to the solvent (ST20), a capping agent for inducing wire formation is added to the solvent. If the reduction for forming the nanowire is made too fast, it is difficult to form a wire shape as the metals are agglomerated, and the capping agent prevents agglomeration and induces growth of the nanowires by allowing the materials in the solvent to be properly dispersed. do.

The capping agent may include a first capping agent and a second capping agent.

The first capping agent comprises a polymer of a first molecular weight. The second capping agent also includes a polymer of a second molecular weight that is greater than the first molecular weight. That is, the molecular weight of the first capping agent is smaller than the molecular weight of the second capping agent.

The same polymer may be used as the first capping agent and the second capping agent. Alternatively, different polymers may be used as the first capping agent and the second capping agent.

Examples of the polymer used as the first capping agent and the second capping agent may include polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polyacrylamide (PAA), and the like.

The first molecular weight polymer may have a weight average molecular weight of about 40000 to 80000. The second molecular weight polymer may have a weight average molecular weight of about 240000 to about 450000.

In particular, the polymer of the first molecular weight and the polymer of the second molecular weight may be polyvinylpyrrolidone. More specifically, the first capping agent may be polyvinylpyrrolidone having a weight average molecular weight of about 40000 to about 80000, and the second capping agent may be polyvinylpyrrolidone having a weight average molecular weight of about 240000 to about 450000 have.

The mass ratio of the first capping agent and the second capping agent may be about 2: 1 to about 8: 1. In more detail, in the capping agent, the first capping agent may be about 70 wt% to about 90 wt%, and the second capping agent may be about 10 wt% to about 30 wt%.

In particular, the capping agent comprises polyvinylpyrrolidone having a weight average molecular weight of about 40000 to about 80000 and polyvinylpyrrolidone having a weight average molecular weight of about 40000 to about 80000 of about 2: 1 to about 8: 1. It can be included as a ratio. More specifically, in the capping agent, the polyvinylpyrrolidone having a weight average molecular weight of about 40000 to about 80000 is about 70 wt% to about 90 wt%, and the polyvinylpyrrolidone having a weight average molecular weight of about 40000 to about 80000 May be from about 10 wt% to about 30 wt%.

The first capping agent comprises a polymer having a relatively small first molecular weight. Accordingly, metal nanowires having a thin diameter may be formed by the first capping agent. The second capping agent also includes a polymer having a relatively large second molecular weight. Accordingly, metal nanowires having a long length may be formed by the second capping agent. That is, the elongated metal nanowires may be formed by the first capping agent and the second capping agent.

For example, the polymer having the first molecular weight and the polymer having the second molecular weight may have a helical structure. In this case, the polymer having the second molecular weight may be extended in a spiral structure of a large diameter. In addition, the polymer having the first molecular weight may be shortly extended into a spiral structure of a small diameter. In this case, several molecules of the polymer having the first molecular weight may be disposed in one molecule of the polymer having the second molecular weight, thereby forming a complex. Such a composite has a small inner diameter and may have a long length. Elongated metal nanowires may be formed in such a composite.

Subsequently, in the step of adding the catalyst to the solvent (ST30), sun salt, purified salt or a halogen metal such as AgCl, PtCl ₂ , PdCl ₂ , AuCl ₃ is added as a catalyst. Such a catalyst has various metals or halogen elements to serve to promote reaction of seed formation and metal nanowire formation for forming metal nanowires.

Subsequently, in the step (ST40) of adding the metal compound to the solvent, the metal compound is added to the solvent to form a reaction solution.

In this case, the metal compound may be added to a solvent to which a capping agent and a catalyst are added while dissolved in a separate solvent. As a separate solvent, the same material or different materials as the solvent used for the first time may be used. And, the metal compound may be added after a certain time after the addition of the catalyst. This is to stabilize the temperature to an appropriate reaction temperature.

Here, the metal compound is a compound containing a metal for forming the metal nanowires to be manufactured. In order to form silver nanowires, AgCl, AgNO ₃ or KAg (CN) ₂ may be used as the metal compound.

 As such, when the metal compound is added to the solvent to which the capping agent and the catalyst are added, the reaction occurs and the formation of the metal nanowires begins.

In the present embodiment, the capping agent may be added by 60 to 330 parts by weight based on 100 parts by weight of a metal compound such as AgCl, AgNO ₃ or KAg (CN) ₂ . When the capping agent is added in less than 60 parts by weight, the agglomeration phenomenon cannot be prevented sufficiently. When the capping agent is added in excess of 330 parts by weight, metal nanoparticles such as spherical and cubic shapes may be formed, and the capping agent may remain on the manufactured metal nanowires to reduce electrical conductivity.

And the catalyst may be added by 0.005 to 0.5 parts by weight based on 100 parts by weight of the metal compound. If the catalyst is added at less than 0.005 parts by weight, the reaction cannot be sufficiently promoted. When the catalyst is added in excess of 0.5 parts by weight, the reduction of silver proceeds rapidly to generate silver nanoparticles, or to increase the diameter of the nanowire and to shorten the length thereof. It may lower the conductivity.

Subsequently, in the step of further adding a solvent at room temperature to the reaction solution (ST50), a solvent at room temperature is further added to the solvent at which the reaction is started. The solvent at room temperature may use the same material or different materials as the solvent used for the first time. For example, polyols such as ethylene glycol and propylene glycol may be used as the solvent at room temperature.

The temperature of the solvent may be increased during the reaction by continuously heating the solvent to maintain a constant reaction temperature. As described above, by adding a solvent at room temperature to the solvent at which the reaction is started, the temperature of the solvent is temporarily lowered. The temperature can be kept more constant.

Further adding the solvent at room temperature (ST50) may be performed once or several times in consideration of the reaction time, the temperature of the reaction solution.

Subsequently, the step of purifying the nanowires (ST60) is to collect and collect the metal nanowires in the reaction solution.

More specifically, when acetone, which is a nonpolar solvent than water, is added to the reaction solution, the metal nanowires are precipitated under the solution by the capping agent remaining on the surface of the metal nanowires. This is because the capping agent dissolves well in the solvent but does not dissolve in acetone, but aggregates and precipitates. Subsequently, the supernatant solution is discarded to remove some of the capping agent and the formed nanoparticles.

When the distilled water is added to the remaining solution, the metal nanowires and the metal nanoparticles are dispersed, and when acetone or the like is added, the metal nanowires are precipitated and the metal nanoparticles are dispersed in the upper solution. Subsequently, the supernatant solution is discarded to remove some of the capping agent and the metal nanoparticles formed by aggregation. This process is repeated to collect the metal nanowires and store them in distilled water. By storing the metal nanowires in distilled water, it is possible to prevent the metal nanowires from reaggregating.

As described above, the nanowire manufacturing method according to the embodiment uses a first capping agent including a polymer having the first molecular weight and a second capping agent including a polymer having the second molecular weight.

At this time, the length of the metal nanowires is increased by the second capping agent having a relatively large molecular weight, and at the same time, the diameter of the metal nanowires may be thinned by the first capping agent having a relatively small molecular weight. have.

That is, the metal nanowires may be formed to be thin and long by the first capping agent and the second capping agent. Accordingly, the nanowire manufacturing method according to the embodiment can provide a metal nanowire having a large aspect ratio.

For example, the metal nanowires formed according to the embodiment may have a diameter of about 60 nm or less and a length of about 20 μm or more. More specifically, the metal nanowires formed according to the embodiment may have a diameter of about 30 nm to about 60 nm, and may have a length of about 20 μm to about 60 μm. In more detail, the metal nanowire according to the embodiment may have a diameter of about 54 nm to about 56 nm, and may have a length of about 30 μm to about 40 μm.

Accordingly, the metal nanowires formed according to the embodiment may have an aspect ratio of about 330 or more. In more detail, the metal nanowires formed in accordance with an embodiment may have an aspect ratio of about 330 to about 2000.

Therefore, the metal nanowires formed according to the present embodiment may have high optical and electrical properties when used in electrodes or the like. That is, the metal nanowire itself according to the present embodiment may be configured as an electrode in a network structure. At this time, since the metal nanowires according to the present embodiment are thin and long, the transmittance and transparency can be increased, and the resistance can be reduced.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the examples are only for illustrating the present invention, and the present invention is not limited thereto.

Example

Ethylene glycol and propylene glycol were mixed at a ratio of about 1: 2 to form about 2000 ml of ethylene glycol solvent. The solvent is heated to about 130 ° C., dissolved by addition of 10 g polyvinylpyrrolidone (molecular weight 40000-80000) and 57 g polyvinylpyrrolidone (molecular weight 240000-450000), followed by 0.75 g KBr and 2.25 g AgCl Was added. After about 1 hour and 30 minutes, about 17 g of AgNO ₃ was dissolved in 1000 ml of ethylene glycol and added to a mixed solution of polyvinylpyrrolidone, KBr and solvent. After that, the reaction was continued for about 1 hour and 30 minutes to complete formation of the silver nanowires.

12000 ml of acetone was added to the reaction solution, and the upper solution containing ethylene glycol, propylene glycol, and silver nanoparticles was discarded.

1000 ml of distilled water was added to disperse the aggregated silver nanowires and silver nanoparticles. Then, 4000 ml of acetone was added, and then the upper layer solution in which ethylene glycol and propylene glycol and silver nanoparticles were dispersed was discarded. This process was repeated three times and stored in 1000 ml of distilled water.

Comparative example

It proceeded under the same conditions as the experimental example except that 67.0 g of polyvinylpyrrolidone (molecular weight 44000-58000) was used as the capping agent and no polyvinylpyrrolidone having a molecular weight of 280000-360000 was used.

result

As shown in Table 1, Figure 2 and Figure 3, in the case of the experimental example, while having a diameter similar to the comparative example, a silver nanowire having a longer length was formed.

Length diameter Experimental Example 45㎛ 55 nm Comparative example 20 탆 50 nm

Features, structures, effects, and the like described in the above description are included in at least one embodiment of the present invention, and are not necessarily limited to only one embodiment. In addition, the features, structures, effects, and the like illustrated in the embodiments may be combined or modified with respect to other embodiments by those skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be construed as limiting the scope of the present invention. It can be seen that various modifications and applications are possible. For example, each component specifically shown in the embodiments may be modified. It is to be understood that the present invention may be embodied in many other specific forms without departing from the spirit or essential characteristics thereof.

Claims (9)

Adding a metal compound and a capping agent to the solvent and heating to form a metal nanowire,
The capping agent
A first capping agent comprising a polymer of a first molecular weight; And
And a second capping agent comprising a polymer having a second molecular weight greater than the first molecular weight. The method of claim 1, wherein the polymer of the first molecular weight and the polymer of the second molecular weight are polyvinylpyrrolidone. The method of claim 2, wherein the first molecular weight is 40000 to 80000, and the second molecular weight is 240000 to 450000. The method of claim 3, wherein the ratio of the polymer of the first molecular weight and the polymer of the second molecular weight is 2: 1 to 8: 1. The method of claim 1, wherein the solvent is heated to a temperature of 110 ° C. to 160 ° C. 6. The method of claim 1, wherein the metal nanowires have a diameter of 30 nm to 60 nm, and the metal nano wires have a length of 20 μm to 60 μm. The method of claim 1, wherein the metal compound is a silver compound. A nanowire having a diameter of 54 nm to 56 nm, a length of 30 m to 60 m, an aspect ratio of 330 to 2000, and a metal. The nanowire of claim 8, wherein the metal is silver.

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